The present invention relates to an image pickup device, a digital photographing device using the image pickup device, an auto-focusing method, and a computer-readable storage medium for performing the auto-focusing method.
Auto-focusing (AF) systems are widely used in photographing apparatuses such as digital compact cameras, lens-changeable cameras, camcorders, or the like. AF systems may be classified into either phase difference AF systems using phase difference detection or contrast AF systems using contrast detection.
A phase difference AF system includes a phase difference AF sensor separate from an image pickup device, and performs AF using a defocus amount of a lens calculated from an output of the phase difference AF sensor. For phase difference AF, an additional mirror for the phase difference AF is required. For example, to apply phase difference AF to a digital single lens reflection (DSLR) camera, a sub-mirror for guiding incident light onto the phase difference AF sensor is further used along with a main mirror. Phase difference AF ensures high-speed, high-performance AF, but is costly due to an extra optical system needed for the phase difference AF.
A contrast AF system extracts high-frequency data from image data output from an image pickup device and controls AF to maximize the high-frequency component. To this end, the contrast AF system requires a signal processing circuit, but no extra sensor or optical system, and thus may be established at relatively low costs. However, the contrast AF system is low in speed and precision relative to phase difference AF systems.